Tom Delworth

Decadal-scale changes in the Atlantic Ocean - natural variability and human-induced climate change

The Atlantic Ocean is an integral component of the global climate system, transporting in excess of 1 PW of heat poleward. It is anticipated that fluctuations or changes in that heat transport might have important climatic impacts. Here we review observational estimates of past variability and change in the Atlantic, including recent rapid warming. Part of the decadal scale variability in the Atlantic appears to be associated with natural variability of the ocean circulation, modulating the transport of heat poleward, and having a significant impact on the atmosphere. This impact includes modulation of the African and Indian monsoonal systems, tropical Atlantic atmospheric circulation changes of relevance for hurricanes, and an influence on summer climate over North America and Western Europe. While natural variability may have contributed to the most recent rapid warming, a substantial fraction of the recent warming is likely attributable to human-induced climate change. Future projections of Atlantic change are influenced by both anthropogenic forcing and natural variability.